The present invention relates to counterbalanced arm assemblies, and more particularly to an articulable spring counterbalanced arm support mechanism for televisions, computer monitors, medical equipment, lamps or the like.
Counterbalanced or equipoised arm assemblies for various purposes have been used for many years. Such counterbalanced arm assemblies are shown, for example, in U.S. Pat. Nos. 2,787,434; 3,041,060; 3,226,073; 3,543,019; 3,774,873; 4,080,530; 4,160,536 and 4,494,177.
In counterbalanced arm assemblies of the type shown in the above-mentioned patents, it is generally desirable that the lower arm connected to the support bracket be capable of pivoting or tilting back and forth to an angle of about 60.degree. on either side of the vertical. Prior devices, such as those disclosed in the above patents, permit this type of movement while balancing the pivoted arm. As can be seen from the above-noted patents, the counterbalancing is achieved with one or more relatively long springs. In double arm constructions, this counterbalancing is traditionally done with one spring on either side of the pivoting arm. However, aesthetic and hygienic requirements often make it desirable to have the spring enclosed within the arm as shown in the later patents. However, this confinement of the spring within the arm makes it difficult to obtain proper balancing leverage and torque because the distance from the pivoting point of the arm to the point on the arm where the spring is connected is restricted.
It is aesthetically and hygienically desirable to enclose the entire counterbalancing mechanism within a hollow interior of and outer arm such as is disclosed in U.S. Pat. Nos. 4,080,530 and 4,494,177. While such an arrangement is aesthetically and hygienically appealing, it is even more difficult than in merely enclosed spring arrangements to obtain the necessary balancing leverage and torque, because the lever arm for producing such forces is limited by the size (i.e. the diameter or width) of the outer arm. Support of relatively heavy objects, such as televisions or computer monitors is very difficult with this conventional arrangement unless excessively heavy springs and excessively large diameter or width support arms are used. Still further, when the weight of the object to be supported by the arm is not precisely known, it is not possible to set the counterbalancing spring force at the factory during manufacture of the counterbalancing arm, and some means of adjusting the spring tension must be provided. Prior means of adjusting the spring tension have required considerable trial and error until the correct balancing tension is obtained.